Synthesis, characterization and thermodynamics of complex formation of some new Schiff base ligands with some transition metal ions and the adduct formation of zinc Schiff base complexes with some organotin chlorides

Abstract

Four new complexes, [M(Salpyr)] where Salpyr=N,N′-bis(Salicylidene)-2,3- and 3,4-diiminopyridine and M=Co, Cu, Mn, Ni and Zn were synthesized and characterized by 1H NMR, IR spectroscopy, elemental analysis and UV–vis spectrophotometry. UV–vis spectrophotometric study of the adduct formation of the zinc(II) complexes, [Zn(2,3-Salpyr)] and [Zn(3,4-Salpyr)], as donor with R2SnCl2 (R=methyl, phenyl, n-butyl), PhSnCl3 and Bu3SnCl as acceptors has been investigated in methanol, as solvent. The formation constants and the thermodynamic free energies were measured using UV–vis spectrophotometry. Titration of the organotin chlorides with Zn(II) complexes at various temperatures (T=283–313K) leads to 1:1 adduct formation. The results show that the formation constants were decreased by increasing the temperature. The trend of the reaction of RnSnCl4−n as acceptors toward given zinc complexes was as follows:PhSnCl3>Me2SnCl2>Ph2SnCl2>Bu2SnCl2>Bu3SnClBy considering the formation constants and the ΔG° of the complex formation for the Schiff base as donor and the M(II) as acceptor, the following conclusion was drawn: the formation constant for a given Schiff base changes according to the following trend:Ni>Cu>Co>Zn>Mn